Israeli forces raided a refugee camp in the northern occupied West Bank, killing at least six Palestinians, Palestinian health authorities said early Wednesday. The Israeli military had also expanded its ground offensive in the Gaza Strip to the densely populated urban refugee camps in the central part of the territory Tuesday.

Residents reported shelling and airstrikes shaking the Nuseirat, Maghazi and Bureij camps in the tiny, cramped enclave. The built-up towns hold Palestinians whose families fled or were driven from their homes in what is now Israel during the 1948 war surrounding Israel’s independence. The camps are now crowded with Palestinians who fled northern Gaza in the early stages of Israel’s ground offensive.